Which statement best describes the relationship between temperature and the density of most substances?

• A. Density and temperature are always directly proportional.
• B. Temperature has no effect on the density of a substance.
• C. As temperature increases, density generally decreases.
• D. As temperature increases, density generally increases.

Answer: (C)

Verified step by step guidance

1. Recall the definition of density, which is mass per unit volume, expressed as \(\text{density} = \frac{\text{mass}}{\text{volume}}\).
2. Understand that when temperature increases, most substances expand, meaning their volume increases while their mass remains constant.
3. Since mass stays the same and volume increases, the density, which is mass divided by volume, will decrease as temperature increases.
4. Recognize that this inverse relationship between temperature and density is typical for most substances, especially liquids and solids.
5. Therefore, the best description is: as temperature increases, density generally decreases.